Data Center Colocation Market Size and Forecast 2021-2031, Global and Regional Share, Trend, and Growth Opportunity Analysis Report Coverage: By Type, Enterprise Size, Industry Vertical, and Region

List of Tables

The Data Center Colocation market size was valued at US$ 74.13 billion in 2024 and is expected to reach US$ 182.58 billion by 2031; it is estimated to record a CAGR of 13.7% from 2025 to 2031.

South and Central America is segmented into Brazil, Argentina, and the Rest of SAM. The South and Central America data center colocation market is at an inflection point. Data center electricity consumption remains relatively modest, often below 1% of total national energy demand. However, growing urbanization, cloud migration, and e-government initiatives are accelerating demand across major economies such as Brazil, Mexico, and Chile. Government policies are increasingly supportive. Brazil's energy regulators and environmental agencies are encouraging renewable power for industrial and digital infrastructure. Countries align with the Paris Agreement targets by implementing incentives to expand solar and wind energy capacity. For instance, Brazil aims to have renewable energy account for over 50 % of its electricity mix by mid-2030s, boosting the availability of green power for colocation operators. Key drivers include enterprise demand for latency-sensitive services in regional hubs like Sao Paulo, along with multinationals' requirements for data residency. These dynamics are encouraging both global hyperscalers and regional providers to expand their footprint via colocation. Regionwide, the business narrative is clear. The growing digital economies, sustainability commitments, and rising enterprise cloud penetration are converging to drive data center colocation market growth. Providers that can reliably scale green power, offer efficient PUE ratings, and comply with environmental regulations will gain a strategic advantage in this emerging landscape.

Brazil holds a key position in the global data center colocation market, supported by its large digital economy, improving connectivity, and regulatory reforms. The Brazilian Internet Steering Committee (CGI.br) reports that internet penetration exceeds 80%, with rising demand for cloud and streaming services. The National Bank for Economic and Social Development (BNDES) is investing in digital infrastructure, including submarine cables such as EllaLink, which enhance Brazil's global connectivity. Due to their reliable power supply and robust fiber networks, Sao Paulo, Rio de Janeiro, and Fortaleza have emerged as key colocation hubs. Brazil's General Data Protection Law (LGPD), which aligns closely with the EU's GDPR, is driving corporate demand for compliant colocation solutions. Additionally, the Ministry of Mines and Energy highlights Brazil's renewable energy matrix (over 80% from hydro, wind, and solar), supporting sustainable data center operations. The Central Bank of Brazil also notes rapid fintech growth, driving the demand for low-latency, secure colocation facilities.

CoreSite Realty Corporation, CyrusOne Inc, Iron Mountain Inc, Digital Realty Trust Inc, Equinix Inc, Telehouse, NTT Data Corp, International Business Machines Corp, Rittal GmbH & Co KG, and ATandT are among the key Data Center Colocation market players that are profiled in this market study.

The overall Data Center Colocation market size has been derived using both primary and secondary sources. Exhaustive secondary research has been conducted using internal and external sources to obtain qualitative and quantitative information related to the Data Center Colocation market size. The process also helps obtain an overview and forecast of the market with respect to all the market segments. Also, multiple primary interviews have been conducted with industry participants to validate the data and gain analytical insights. This process includes industry experts such as VPs, business development managers, market intelligence managers, and national sales managers, along with external consultants such as valuation experts, research analysts, and key opinion leaders, specializing in the Data Center Colocation market.

Product Code: TIPTE100000210

1. Introduction

1.1 Report Guidance
1.2 Market Segmentation

2. Executive Summary

2.1 Analyst Market Outlook
2.2 Market Attractiveness

3. Research Methodology

3.1 Secondary Research
3.2 Primary Research
- 3.2.1 Hypothesis formulation:
- 3.2.2 Macro-economic factor analysis:
- 3.2.3 Developing base number:
- 3.2.4 Data Triangulation:
- 3.2.5 Country level data:
3.3 Assumptions and Limitations

4. Data Center Colocation Market Landscape

4.1 Overview
4.2 PEST Analysis
4.3 Ecosystem Analysis
- 4.3.1 Component Providers:
- 4.3.2 Manufacturers:
- 4.3.3 Distributors or Suppliers:
- 4.3.4 End-Users:
- 4.3.5 List of Vendors in Value Chain:

5. Data Center Colocation Market - Key Market Dynamics

5.1 Data Center Colocation Market - Key Market Dynamics
5.2 Market Drivers
- 5.2.1 Rise in Demand for Scalable IT Infrastructure
- 5.2.2 Global Data Traffic Surge and Acceleration of Digital Transformation
- 5.2.3 Surging Data Generation
5.3 Market Restraints
- 5.3.1 High Initial and Maintenance Costs
- 5.3.2 Security and Compliance Risks
- 5.3.3 Limited Customization
5.4 Market Opportunities
- 5.4.1 Rise of Hybrid and Multi-Cloud Adoption
- 5.4.2 Regulatory Compliance and Data Sovereignty
- 5.4.3 Rise in AI and HPC Workloads
5.5 Future Trends
- 5.5.1 Sustainability and Green Energy
- 5.5.2 Increase in Demand for Artificial Intelligence in Infrastructure
- 5.5.3 Adoption of Modular and Prefabricated Builds
5.6 Impact of Drivers and Restraints:

6. Data Center Colocation Market - Global Market Analysis

6.1 Data Center Colocation Market Revenue (US$ Million), 2021-2031
6.2 Data Center Colocation Market Forecast Analysis

7. Data Center Colocation Market Analysis - by Type

7.1 Retail Colocation
- 7.1.1 Overview
- 7.1.2 Retail Colocation: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)
7.2 Wholesale Colocation
- 7.2.1 Overview
- 7.2.2 Wholesale Colocation: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)
7.3 Hybrid Cloud-based Colocation
- 7.3.1 Overview
- 7.3.2 Hybrid Cloud-based Colocation: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)

8. Data Center Colocation Market Analysis - by Enterprise Size

8.1 Large Enterprises
- 8.1.1 Overview
- 8.1.2 Large Enterprises: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)
8.2 SMEs
- 8.2.1 Overview
- 8.2.2 SMEs: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)

9. Data Center Colocation Market Analysis - by Industry Vertical

9.1 IT and Telecom
- 9.1.1 Overview
- 9.1.2 IT and Telecom: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)
9.2 BFSI
- 9.2.1 Overview
- 9.2.2 BFSI: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)
9.3 Healthcare
- 9.3.1 Overview
- 9.3.2 Healthcare: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)
9.4 Retail
- 9.4.1 Overview
- 9.4.2 Retail: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)
9.5 Others
- 9.5.1 Overview
- 9.5.2 Others: Data Center Colocation Market - Revenue and Forecast to 2031 (US$ Million)

10. Data Center Colocation Market - Geographical Analysis

10.1 Overview
10.2 North America
- 10.2.1 North America Data Center Colocation Market Overview
- 10.2.2 North America: Data Center Colocation Market - Revenue, 2021-2031 (US$ Million)
- 10.2.3 North America: Data Center Colocation Market Breakdown, by Type
  - 10.2.3.1 North America: Data Center Colocation Market - Revenue and Forecast Analysis - by Type
- 10.2.4 North America: Data Center Colocation Market Breakdown, by Enterprise Size
  - 10.2.4.1 North America: Data Center Colocation Market - Revenue and Forecast Analysis - by Enterprise Size
- 10.2.5 North America: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.2.5.1 North America: Data Center Colocation Market - Revenue and Forecast Analysis - by Industry Vertical
- 10.2.6 North America: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.2.6.1 North America: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.2.6.2 United States: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.2.6.2.1 United States: Data Center Colocation Market Breakdown, by Type
    - 10.2.6.2.2 United States: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.2.6.2.3 United States: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.2.6.3 Canada: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.2.6.3.1 Canada: Data Center Colocation Market Breakdown, by Type
    - 10.2.6.3.2 Canada: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.2.6.3.3 Canada: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.2.6.4 Mexico: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.2.6.4.1 Mexico: Data Center Colocation Market Breakdown, by Type
    - 10.2.6.4.2 Mexico: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.2.6.4.3 Mexico: Data Center Colocation Market Breakdown, by Industry Vertical
10.3 Europe
- 10.3.1 Europe Data Center Colocation Market Overview
- 10.3.2 Europe: Data Center Colocation Market - Revenue, 2021-2031 (US$ Million)
- 10.3.3 Europe: Data Center Colocation Market Breakdown, by Type
  - 10.3.3.1 Europe: Data Center Colocation Market - Revenue and Forecast Analysis - by Type
- 10.3.4 Europe: Data Center Colocation Market Breakdown, by Enterprise Size
  - 10.3.4.1 Europe: Data Center Colocation Market - Revenue and Forecast Analysis - by Enterprise Size
- 10.3.5 Europe: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.3.5.1 Europe: Data Center Colocation Market - Revenue and Forecast Analysis - by Industry Vertical
- 10.3.6 Europe: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.3.6.1 Europe: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.3.6.2 Germany: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.3.6.2.1 Germany: Data Center Colocation Market Breakdown, by Type
    - 10.3.6.2.2 Germany: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.3.6.2.3 Germany: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.3.6.3 France: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.3.6.3.1 France: Data Center Colocation Market Breakdown, by Type
    - 10.3.6.3.2 France: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.3.6.3.3 France: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.3.6.4 Italy: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.3.6.4.1 Italy: Data Center Colocation Market Breakdown, by Type
    - 10.3.6.4.2 Italy: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.3.6.4.3 Italy: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.3.6.5 United Kingdom: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.3.6.5.1 United Kingdom: Data Center Colocation Market Breakdown, by Type
    - 10.3.6.5.2 United Kingdom: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.3.6.5.3 United Kingdom: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.3.6.6 Russia: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.3.6.6.1 Russia: Data Center Colocation Market Breakdown, by Type
    - 10.3.6.6.2 Russia: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.3.6.6.3 Russia: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.3.6.7 Rest of Europe: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.3.6.7.1 Rest of Europe: Data Center Colocation Market Breakdown, by Type
    - 10.3.6.7.2 Rest of Europe: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.3.6.7.3 Rest of Europe: Data Center Colocation Market Breakdown, by Industry Vertical
10.4 Asia Pacific
- 10.4.1 Asia Pacific Data Center Colocation Market Overview
- 10.4.2 Asia Pacific: Data Center Colocation Market - Revenue, 2021-2031 (US$ Million)
- 10.4.3 Asia Pacific: Data Center Colocation Market Breakdown, by Type
  - 10.4.3.1 Asia Pacific: Data Center Colocation Market - Revenue and Forecast Analysis - by Type
- 10.4.4 Asia Pacific: Data Center Colocation Market Breakdown, by Enterprise Size
  - 10.4.4.1 Asia Pacific: Data Center Colocation Market - Revenue and Forecast Analysis - by Enterprise Size
- 10.4.5 Asia Pacific: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.4.5.1 Asia Pacific: Data Center Colocation Market - Revenue and Forecast Analysis - by Industry Vertical
- 10.4.6 Asia Pacific: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.4.6.1 Asia Pacific: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.4.6.2 Australia: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.4.6.2.1 Australia: Data Center Colocation Market Breakdown, by Type
    - 10.4.6.2.2 Australia: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.4.6.2.3 Australia: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.4.6.3 China: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.4.6.3.1 China: Data Center Colocation Market Breakdown, by Type
    - 10.4.6.3.2 China: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.4.6.3.3 China: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.4.6.4 Japan: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.4.6.4.1 Japan: Data Center Colocation Market Breakdown, by Type
    - 10.4.6.4.2 Japan: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.4.6.4.3 Japan: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.4.6.5 India: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.4.6.5.1 India: Data Center Colocation Market Breakdown, by Type
    - 10.4.6.5.2 India: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.4.6.5.3 India: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.4.6.6 South Korea: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.4.6.6.1 South Korea: Data Center Colocation Market Breakdown, by Type
    - 10.4.6.6.2 South Korea: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.4.6.6.3 South Korea: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.4.6.7 Rest of APAC: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.4.6.7.1 Rest of APAC: Data Center Colocation Market Breakdown, by Type
    - 10.4.6.7.2 Rest of APAC: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.4.6.7.3 Rest of APAC: Data Center Colocation Market Breakdown, by Industry Vertical
10.5 Middle East and Africa
- 10.5.1 Middle East and Africa Data Center Colocation Market Overview
- 10.5.2 Middle East and Africa: Data Center Colocation Market - Revenue, 2021-2031 (US$ Million)
- 10.5.3 Middle East and Africa: Data Center Colocation Market Breakdown, by Type
  - 10.5.3.1 Middle East and Africa: Data Center Colocation Market - Revenue and Forecast Analysis - by Type
- 10.5.4 Middle East and Africa: Data Center Colocation Market Breakdown, by Enterprise Size
  - 10.5.4.1 Middle East and Africa: Data Center Colocation Market - Revenue and Forecast Analysis - by Enterprise Size
- 10.5.5 Middle East and Africa: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.5.5.1 Middle East and Africa: Data Center Colocation Market - Revenue and Forecast Analysis - by Industry Vertical
- 10.5.6 Middle East and Africa: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.5.6.1 Middle East and Africa: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.5.6.2 South Africa: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.5.6.2.1 South Africa: Data Center Colocation Market Breakdown, by Type
    - 10.5.6.2.2 South Africa: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.5.6.2.3 South Africa: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.5.6.3 Saudi Arabia: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.5.6.3.1 Saudi Arabia: Data Center Colocation Market Breakdown, by Type
    - 10.5.6.3.2 Saudi Arabia: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.5.6.3.3 Saudi Arabia: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.5.6.4 United Arab Emirates: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.5.6.4.1 United Arab Emirates: Data Center Colocation Market Breakdown, by Type
    - 10.5.6.4.2 United Arab Emirates: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.5.6.4.3 United Arab Emirates: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.5.6.5 Rest of Middle East and Africa: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.5.6.5.1 Rest of Middle East and Africa: Data Center Colocation Market Breakdown, by Type
    - 10.5.6.5.2 Rest of Middle East and Africa: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.5.6.5.3 Rest of Middle East and Africa: Data Center Colocation Market Breakdown, by Industry Vertical
10.6 South and Central America
- 10.6.1 South and Central America Data Center Colocation Market Overview
- 10.6.2 South and Central America: Data Center Colocation Market - Revenue, 2021-2031 (US$ Million)
- 10.6.3 South and Central America: Data Center Colocation Market Breakdown, by Type
  - 10.6.3.1 South and Central America: Data Center Colocation Market - Revenue and Forecast Analysis - by Type
- 10.6.4 South and Central America: Data Center Colocation Market Breakdown, by Enterprise Size
  - 10.6.4.1 South and Central America: Data Center Colocation Market - Revenue and Forecast Analysis - by Enterprise Size
- 10.6.5 South and Central America: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.6.5.1 South and Central America: Data Center Colocation Market - Revenue and Forecast Analysis - by Industry Vertical
- 10.6.6 South and Central America: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.6.6.1 South and Central America: Data Center Colocation Market - Revenue and Forecast Analysis - by Country
  - 10.6.6.2 Brazil: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.6.6.2.1 Brazil: Data Center Colocation Market Breakdown, by Type
    - 10.6.6.2.2 Brazil: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.6.6.2.3 Brazil: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.6.6.3 Argentina: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.6.6.3.1 Argentina: Data Center Colocation Market Breakdown, by Type
    - 10.6.6.3.2 Argentina: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.6.6.3.3 Argentina: Data Center Colocation Market Breakdown, by Industry Vertical
  - 10.6.6.4 Rest of South and Central America: Data Center Colocation Market - Revenue and Forecast, 2021-2031 (US$ Million)
    - 10.6.6.4.1 Rest of South and Central America: Data Center Colocation Market Breakdown, by Type
    - 10.6.6.4.2 Rest of South and Central America: Data Center Colocation Market Breakdown, by Enterprise Size
    - 10.6.6.4.3 Rest of South and Central America: Data Center Colocation Market Breakdown, by Industry Vertical

11. Competitive Landscape

11.1 Heat Map Analysis by Key Players
11.2 Company Market Share Analysis, 2024

12. Industry Landscape

12.1 Overview
12.2 Market Initiatives
12.3 New Product Development
12.4 Partnerships and Collaboration

13. Company Profiles

13.1 CoreSite Realty Corporation
- 13.1.1 Key Facts
- 13.1.2 Business Description
- 13.1.3 Products and Services
- 13.1.4 Financial Overview
- 13.1.5 SWOT Analysis
- 13.1.6 Key Developments
13.2 CyrusOne Inc
- 13.2.1 Key Facts
- 13.2.2 Business Description
- 13.2.3 Products and Services
- 13.2.4 Financial Overview
- 13.2.5 SWOT Analysis
- 13.2.6 Key Developments
13.3 Iron Mountain Inc
- 13.3.1 Key Facts
- 13.3.2 Business Description
- 13.3.3 Products and Services
- 13.3.4 Financial Overview
- 13.3.5 SWOT Analysis
- 13.3.6 Key Developments
13.4 Digital Realty Trust Inc
- 13.4.1 Key Facts
- 13.4.2 Business Description
- 13.4.3 Products and Services
- 13.4.4 Financial Overview
- 13.4.5 SWOT Analysis
- 13.4.6 Key Developments
13.5 Equinix Inc
- 13.5.1 Key Facts
- 13.5.2 Business Description
- 13.5.3 Products and Services
- 13.5.4 Financial Overview
- 13.5.5 SWOT Analysis
- 13.5.6 Key Developments
13.6 Telehouse
- 13.6.1 Key Facts
- 13.6.2 Business Description
- 13.6.3 Products and Services
- 13.6.4 Financial Overview
- 13.6.5 SWOT Analysis
- 13.6.6 Key Developments
13.7 NTT Data Corp
- 13.7.1 Key Facts
- 13.7.2 Business Description
- 13.7.3 Products and Services
- 13.7.4 Financial Overview
- 13.7.5 SWOT Analysis
- 13.7.6 Key Developments
13.8 International Business Machines Corp
- 13.8.1 Key Facts
- 13.8.2 Business Description
- 13.8.3 Products and Services
- 13.8.4 Financial Overview
- 13.8.5 SWOT Analysis
- 13.8.6 Key Developments
13.9 Rittal GmbH & Co KG
- 13.9.1 Key Facts
- 13.9.2 Business Description
- 13.9.3 Products and Services
- 13.9.4 Financial Overview
- 13.9.5 SWOT Analysis
- 13.9.6 Key Developments
13.10 AT&T
- 13.10.1 Key Facts
- 13.10.2 Business Description
- 13.10.3 Products and Services
- 13.10.4 Financial Overview
- 13.10.5 SWOT Analysis
- 13.10.6 Key Developments

14. Appendix

14.1 About The Insight Partners
14.2 Word Index